IL21 and neoplasm: We armed VVL-DD with an optimal combination of GM-CSF and IL-21 to create VVLΔTK-GM-CSFΔA49-IL-21 (hereafter, VVL-GL21), and investigated its function in remodeling TME as well as its anti-tumor efficacy when administered either alone or in combination with α-PD1 via intratumoral and intravenous delivery in the PaCa mouse model.